PS 56-11 - How does land ownership affect biodiversity and biomass stocks in secondary tropical dry forests?

Thursday, August 11, 2011
Exhibit Hall 3, Austin Convention Center
Moana L. McClellan, Plant Biological Sciences, University of Minnesota, St. Paul, MN, Rebecca A. Montgomery, Department of Forest Resources, University of Minnesota, St. Paul, MN and Jennifer S. Powers, Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN

Research efforts in tropical forests have tended to focus on protected primary forests. However, given that tropical secondary forests now compose ~50% of tropical forests and much of this forest is located on private lands, it is important to quantify the differences between publicly and privately owned secondary forests. The goal of this study was to assess whether tree biodiversity and biomass of tropical dry secondary forests in Costa Rica differed as a function of land ownership.  Private vs. public landowner management practices may affect dry forest regeneration processes; for example, private landowners often use fire to “clean” or reduce successional growth while public parks repress fire.

We hypothesized that both tree biodiversity and biomass would be lower in private forests due to selective species removal and lower seed source availability in smaller regenerating forest patches on private lands. We identified and measured all trees >10cm DBH in 30 0.1 ha forest plots on privately owned forests, and compared these data to a dataset collected in two public parks. Aboveground biomass in trees > 10cm DBH was calculated using allometric equations that include DBH and species-specific wood density.


Contrary to our predictions, Shannon-Weiner diversity of trees did not differ significantly between private and public forests for stands between 11-20 years (n=5 plots per ownership class) (p = 0.3), although the trend was in the direction we hypothesized. Aboveground biomass for trees >10cm DBH was also not significantly different between public and private ownership classes for the young age class (n = 5 plots per ownership) (p = 0.2).  While there were no overall differences in biomass and diversity between public and private forests between 11-20 years, we speculate that there may be differences in older secondary forest (between 20-30, 31-40, and >40 years) due to landowner management objectives such as selective harvests.

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